Hybrid follicular cyst (pilomatrical and infundibular) arising within a sebaceous nevus

Cutaneous Adnexal Cysts Revisited: What We Know and What We Think We Know

Cutaneous cysts have been classified by dermatopathologists in many different ways. Here, we propose a novel classification of cutaneous adnexal cysts according to their origin in the folliculosebaceous unit and the sweat glands. By examining the lining of the cystic structure, its origin can be easily identified. Epidermal cysts have an epithelial wall containing a granular layer with lamellar keratinization, indicating an infundibular origin. Tricholemmal cysts have an undulating epithelial wall with no granular layer and a compact keratinization, showing an isthmic origin. In steatocystoma, dermoid cyst, and folliculosebaceous hamartoma, the epithelial lining shows a crenulated appearance which is seen in the sebaceous duct. Hidrocystoma shows the characteristic cuboidal epithelial lining of sweat glands with decapitation secretion in its apocrine forms. The hair matrix cyst wall is composed of basaloid cells maturing to squamoid cells, as seen in the normal hair matrix and shadow cells in the lumen. Metabolizing acquired dioxin-induced skin hamartoma (MADISH) is a cystic lesion with lamellar keratinization, and no sebaceous glands. The classification proposed here aims to simplify the complexity of cutaneous adnexal cysts, and to facilitate a better understanding of the origin of cystic lesions of the skin.

A Rare Entity of Giant Epidermal Exophytic Naevus of Hemifacial Region

The term nevi constitute a hamartomatous growth of either skin or mucosa that is generally found at birth or shortly after birth. An epidermal nevus consisting chiefly of sebaceous glands is called as nevus sebaceous. Typically this entity is seen as a solitary bald patch over the scalp at birth. We report a case of exophytic lesion following blaschko's lines at birth. We find this case as peculiar because of the multiplicity of lesions, their pattern of distribution, as well as their atypical morphology.

Cutaneous hybrid cyst in a sprague-dawley rat

This report describes a spontaneous hybrid cyst in a Sprague-Dawley (SD) rat. A 52-week-old, male SD rat had a cutaneous cyst on the left mystacial pad. Histologically, the cyst wall showed infundibular differentiation with keratohyalin granules in the granular layer and matrical differentiation comprising basaloid epithelial cells with trichohyalin granules. The cyst cavity was filled with lamellar, flaky keratin and aggregates of shadow cells. Immunohistochemically, the infundibular-type epithelium was positive for cytokeratin (CK) AE1/AE3, CK KL1 and CK14 but negative for CK15, whereas the matrical-type epithelium was negative for all four CK isoforms examined. These immunohistochemical properties of the infundibular- and matrical-type epithelia were similar to those of the infundibulum and inferior segment of normal hair follicles, respectively. Based on these findings, the cyst was diagnosed as a hybrid cyst, comprising more than one type of cyst arising from various parts of the pilosebaceous unit.